The present disclosure relates in general to energy generation and storage systems, and in particular to techniques for facilitating the management of such systems.
In recent years, climate change concerns, federal/state initiatives, and other factors have driven a rapid rise in the installation of renewable energy generation systems (i.e., systems that generate energy using renewable resources such as solar, wind, hydropower, etc.) at residential and non-residential sites. Solar photovoltaic (PV) systems, in particular, have been very popular; in 2011, nearly two gigawatts of PV capacity were installed in the United States, and that number is expected to double in 2012. The majority of this PV capacity is “grid-connected”—in other words, tied to the utility-maintained electrical grid. This allows site loads to be serviced from the grid at times when the PV system cannot generate sufficient energy due to lack of sunlight (e.g., at night), while enabling energy to be fed back into the grid at times when PV energy production exceeds site loads (thereby resulting in, e.g., a credit on the site owner's electricity bill and allowing the benefits of this energy conveyed to others on the grid).
One limitation with grid-connected PV systems is that, unlike a traditional power plant, the PV system power output is intermittent and not dispatchable. This means that the PV system is limited in its ability to provide power capacity at times of peak grid loads. The PV system is also limited in its ability to balance grid voltage and frequency variability, and to supply energy when prices are most economic. Most PV systems are reliant on the presence of a utility grid to operate due to safety regulations in place to protect utility workers, meaning the PV system cannot supply local loads when the utility grid is shut down or otherwise unavailable. Thus, in the case of a grid blackout, such systems cannot act as a backup energy source to power critical site loads, regardless of the amount of sunlight being received at the time of the blackout. To address this, systems have been developed that integrate grid-connected PV components with an on-site energy storage subsystem, such as a battery device and a battery inverter/charger. In these integrated systems, the energy storage subsystem can store excess energy as it is generated by the PV components, and then dispatch the stored energy to satisfy local and grid wide loads as needed. In addition, this energy storage capability enables a number of other features that can provide benefits to the site owner or the installer/service provider of the system, such as the ability to “time shift” energy usage to minimize energy costs and/or earn revenue, or the ability to control instantaneous power demand at a given site.
Despite the advantages associated with integrating grid-connected PV energy generation with on-site energy storage, there are a number of challenges that make it difficult to efficiently deploy and control such integrated systems, particularly on a large, distributed scale. For example, existing PV/energy storage systems typically require manual provisioning by an on-site technician prior to use, which is a time-consuming, cumbersome, and error-prone process. As another example, it is generally beneficial to control the charging and discharging of the energy storage devices in these systems via a central authority (e.g., a remote server administered by the system installer or service provider). However, current implementations do not allow for such control in a flexible and efficient manner. As yet another example, the PV and energy storage components used in existing systems may be supplied by a number of different vendors, each utilizing different vendor-specific communication protocols. This complicates the process of designing control components and algorithms, since the components/algorithms need to interoperate with each of the vendor-specific protocols.